The anatomy and phylogenetic position of the erythrosuchid archosauriform Guchengosuchus shiguaiensis from the earliest Middle Triassic of China.

Richard J Butler,Jun Liu,Roland B Sookias,Corwin Sullivan,Martín D Ezcurra

doi:10.7717/peerj.6435

Abstract

Erythrosuchidae is a clade of early archosauriform reptiles, which were apex predators in many late Early and Middle Triassic ecosystems, following the Permo-Triassic mass extinction. Erythrosuchids had a worldwide distribution, with well-preserved fossil material known from South Africa, European Russia, and China. We here redescribe the anatomy and revise the taxonomy of Guchengosuchus shiguaiensis, which is one of the stratigraphically oldest erythrosuchids and is known from a single partial skeleton from the lowermost Middle Triassic (lower Anisian) lower Ermaying Formation of Shaanxi Province, China. We provide a new differential diagnosis for Guchengosuchus shiguaiensis, and identify a series of autapomorphies relating to the morphologies of the skull roof and vertebrae. Incorporating updated anatomical information for Guchengosuchus into the most comprehensive morphological phylogenetic analysis available for early archosauromorphs recovers it as an early branching member of Erythrosuchidae, outside of the clade formed by Garjainia, Erythrosuchus, Chalishevia, and Shansisuchus. Fugusuchus hejiapanensis, from the uppermost Lower Triassic to lower Middle Triassic Heshanggou Formation of China, is recovered as the earliest branching member of Erythrosuchidae.

Highlights

How to cite this article Butler RJ, Ezcurra MD, Liu J, Sookias RB, Sullivan C. 2019
The phylogenetic relationships of Erythrosuchidae found in our analysis are congruent with those previously recovered by Ezcurra (2016) and Ezcurra et al (2018)
Ghost lineages longer than 3 million years are common among other Permo-Triassic archosauromorph clades, such as rhynchosaurs and allokotosaurs (Nesbitt et al, 2015; Ezcurra, 2016; Sengupta, Ezcurra & Bandyopadhyay, 2017)

Summary

INTRODUCTION

The anatomy and phylogenetic position of the erythrosuchid archosauriform Guchengosuchus shiguaiensis from the earliest Middle Triassic of China. Erythrosuchids were important apex predators in earliest Mesozoic ecosystems, and are characterized by their proportionately large skulls and hypercarnivorous adaptations (Ezcurra, Butler & Gower, 2013). One of the least well–understood erythrosuchids is Guchengosuchus shiguaiensis from the earliest Middle Triassic of Shaanxi, China (Fig. 1). The first inclusion of this species in a quantitative phylogenetic analysis was by Ezcurra (2016), who recovered it as the earliest branching member of the erythrosuchid clade, making it potentially significant for understanding the origins of the distinctive body plan of the group. We provide a full redescription of the anatomy of Guchengosuchus, revise its taxonomy, and discuss its phylogenetic position in more detail

MATERIALS AND METHODS

Findings

DISCUSSION AND CONCLUSION